Various silver halide color photographic materials are commercially available, and various image forming methods using these materials are known for use in various applications. The performance required of a photographic material varies depending on the use thereof, but generally, a photographic material must exhibit high sharpness for good high density image recording which is the most advantageous characteristic of silver halide photographic materials. Various practical methods for increasing sharpness have been developed in accordance with the degree of requirements for photographic materials and intended application.
Primary factors which cause a lowering in the sharpness of the photographic material include two factors, namely, halation caused by reflection of incident light mainly at the interface between the emulsion layer and the support or between the support and air, and irradiation caused by light scattering from the silver halide grains themselves.
The coating of a layer containing a white pigment on a support is effective for enhancing sharpness as disclosed, for example, in JP-B-58-43734 (the term "JP-B" as used herein refers to an "examined Japanese patent publication"), JP-A-58-17433 (the term "JP-A" as used herein refers to a "published unexamined Japanese patent application"), JP-A-58-14830 and JP-A-61-259246. However, effects obtained by these methods are insufficient. Other methods described in U.S. Pat. Nos. 2,548,564 and 3,625,694, JP-A-56-12639, JP-A-63-197943, European Patent 0337490A2 and JP-A-1-188850 concerning the coloring of photographic layers in the photographic material by dyes, etc., are proposed for improving sharpness. However, effects obtained by these methods are also insufficient. It has been found that when the content of the dye is increased to improve sharpness, variation in photographic characteristics is disadvantageously increased when the photographic material is continuously processed.
Stain in the unexposed areas of a silver halide color photographic material is undesirable because it influences the white clearance of image and reduces the distinctiveness of the image from the background. In addition thereto, stain has an adverse effect on the color turbidity of dye image and degrades visual sharpness. Particularly, when the support is composed of a reflective material, the reflection density of stain is considered to be enhanced by several times the transmitted density. Accordingly, even slight staining damages image quality, and, therefore, stain is a very important factor. Four main factors contribute to staining. First, stain is caused by heat or humidity prior to processing but after preparation of the photographic material. Second, stain is caused by the developed fog of the silver halide. Third, stain is caused by color staining (e.g., air fogging) of couplers in developing solutions, or bleaching stain wherein developing agents left in emulsion layers are oxidized by the bleaching bath or oxygen and reacted with couplers to form dyes. Fourth, stain is caused by a change with the passage of time caused by light or humidity after development. A problem to be solved in the present invention is concerned with stain caused by the above third or fourth factors, in particular. The problem of stain has been particularly noted in recent years and is associated with the low rate of replenishment of processing solutions including rinsing solutions now employed to conserve resources and reduce pollution. Methods for alleviating the problem of stain are described, for example, in U.S. Pat. Nos. 3,935,016, 3,960,570 and 2,360,290, JP-A-51-9449 and European Patent 0277589. The present inventors have studied the methods described in the above patent publications and have found that the compounds represented by formulae (I) or (II) and (III) according to the present invention, as described in European Patent 0277589, can remarkably prevent the occurrence of stain from being formed, but result in an unacceptable change in sensitivity and gradation when the photographic materials are continuously processed. The present inventors have also found that when the coating weights of dyes are increased to improve sharpness as described above, the change in sensitivity and gradation after continuous processing is much increased. Thus, the above described methods cannot be applied practically to continuous processing. As a result, the present inventors have extensively studied the problem of enhanced sharpness in continuous processing while still providing stable photographic properties.